⭐ A postage stamp kept below a rectangular glass slab of refractive index 1.5 when viewed from vertically above it, appears to be raised by 7.0 mm. Calculate the thickness of the glass slab.
⭐ The bob of a simple pendulum is imparted a velocity of 5 m/s¹ when it is at its mean position. To what maximum vertical height will it raise on reaching at its extreme position if 60% of its energy is lost in overcoming the friction of air ? ( Take g = 10 m/s² )
Answers
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Explanation:
A postage stamp kept below a rectangular glass slab of refractive index 1.5 when viewed from vertically above it, appears to be raised by 7.0 mm. Calculate the thickness of the glass slab.
ʀᴇғʀᴀᴄᴛɪᴠᴇ ɪɴᴅᴇx ᴏғ ᴛʜᴇ ɢʟᴀss ʙʟᴏᴄᴋ, μɢ = 1.5
sʜɪғᴛ ɪɴ ᴛʜᴇ ɪᴍᴀɢᴇ = 7ᴍᴍ ᴏʀ 0.7 ᴄᴍ
ᴛʜɪᴄᴋɴᴇss ᴏғ ɢʟᴀss ʙʟᴏᴄᴋ ᴏʀ ʀᴇᴀʟ ᴅᴇᴘᴛʜ =?
sʜɪғᴛ = ʀᴇᴀʟ ᴅᴇᴘᴛʜ × (1 - 1/μ) 0.7
= ʀ × (1 - 1/1.5) ʀ
= 0.7 x 1.5/0.5 = 2.1ᴄᴍ
The bob of a simple pendulum is imparted a velocity of 5 m/s¹ when it is at its mean position. To what maximum vertical height will it raise on reaching at its extreme position if 60% of its energy is lost in overcoming the friction of air ? ( Take g = 10 m/s² )
ᴡʜᴇɴ ɪᴛ ɪs ᴀᴛ ᴍᴇᴀɴ ᴘᴏsɪᴛɪᴏɴ ɪᴛ ᴡɪʟʟ ʜᴀᴠᴇ ᴀ ᴋ.ᴇ ᴏғ 0.5ᴍᴠ^2
ᴋ.ᴇ =0.5 ×ᴍ×5×5 = 12.5×ᴍᴊ
60% ᴏғ ᴛʜɪs ᴋ.ᴇ ɪs ʟᴏsᴛ ʜᴇɴᴄᴇ ʀᴇᴍᴀɪɴɪɴɢ ɪs ᴇǫᴜᴀʟ ᴛᴏ (40/100)112.5×ᴍ= 5ᴍ
ᴘ.ᴇ = ᴍɢʜ = 5×ᴍ
ʜ = 5/ɢ = 5/10 = 0.5ᴍ
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